Videos posted online show frustrated motorists blaring their horns as at least five of the taxis, identified by the large black sensors on their roofs, blockaded an intersection.
A Waymo spokesman told local media: “We have temporarily suspended our ride-hailing services given the broad power outage in San Francisco.
“We are focused on keeping our riders safe and ensuring emergency personnel have the clear access they need to do their work.”
Waymo, which also operates in Los Angeles and Phoenix, Arizona, started testing its fleet of robo-taxis in 2021 and made them available to the public in June 2024.
In March, it was reported that the driverless cars racked up nearly 600 parking tickets worth about US$65,000 ($113,000) in San Francisco because they favoured convenience over the rules of the road.
Waymo said at the time it was still refining the taxis’ capabilities.
Daniel Lurie, the Mayor of San Francisco, asked residents to stay indoors because the power cut made travel dangerous. Rail lines have also been shut down.
“If you don’t need to travel tonight, please stay off the roads and stay inside,” he said.
“We will be expanding officer presence at intersections and corridors to ensure the safety of those still on the road.”
Areas hit by the power cut, which is thought to have been caused by a fire at a substation, include Richmond, Sunset, Haight-Ashbury, Hayes Valley, Forest Hill and Golden Gate Park.
Lurie announced at around 10pm local time that power had been restored to around 90,000 people, while 40,000 were still in the dark.
Almost 21,000 people were still without power, according to estimates.
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